In its May 31 analysis, ISS said it had not yet developed a view, from a valuation perspective, on whether the offer from Dish is superior to the SoftBank deal for Sprint shareholders, given the preliminary nature of the Dish offer, and because Dish has not yet made its offer directly through a tender.

Sprint has said it would evaluate the $25.5 billion counter offer from Dish and agreed to let it take a closer look at its books.

ISS said Sprint shareholders should vote for the proposed transaction with SoftBank, given the strategic merits of the SoftBank deal, the sales and negotiation process overseen by the board, the strength of the valuation relative to precedent transactions and the market reaction to the offer.

The SoftBank deal addresses “Sprint’s most compelling need: capital to acquire additional spectrum and complete the transformation of its network,” ISS said, adding that the deal would enable the company to fully compete in the U.S. market.

Sprint said on Saturday it remains focused on finalizing its signed merger agreement with SoftBank, which has been recommended by Sprint’s board of directors. SoftBank said it was pleased that ISS recognized “the value proposition of our agreed transaction and the unique contributions of SoftBank’s proven track record in wireless.”

Dish declined to comment.

Neither Sprint nor Dish have said when they expect Dish’s due diligence process to be completed, but shareholders are hoping for a Sprint comment on the Dish bid before they are due to vote on the SoftBank offer on June 12.

While the Dish deal would add a lot of debt to the combined company’s balance sheet, several big shareholders have said they believe the Dish offer is the more attractive one.

ISS said that while Dish’s proposal offers more per share in cash - $4.76 versus $4.03 in the SoftBank offer - “shareholders cannot ignore the question of execution risk, upon which all assumptions about future value creation must ultimately rest.”

Sprint is also battling Dish to buy out the minority shareholders of Clearwire Corp CLWR.O, in which Sprint already owns a majority stake. ISS made its recommendation for Sprint two days after Dish made a $4.40 per share bid for Clearwire on May 29, challenging Sprint’s offer of $3.40 per share.

Shares of Sprint closed at $7.30 on Friday, May 31.

Reporting By Sinead Carew in New York, writing by Jessica Wohl in Chicago; editing by Gunna Dickson